1. Technical Field
The present invention relates to a driver circuit which generates a drive control signal based on a rotational state signal of a sine wave shape which indicates a rotational state of a motor.
2. Related Art
There exist various motors, and a stepping motor is known as a representative motor which can accurately determine a position and is widely in use in various devices. For example, the stepping motor is used in focusing in a camera, shaking correction, and positioning of a machine tool.
The drive of the stepping motor is normally achieved by changing a rotational position of a rotor with current phases to two stator coils.
There is a demand for minimizing power consumption in an electrical device. In particular, this demand is high in a portable device which is driven with a battery. In driving of the stepping motor, the currents supplied to two coils differ in phase by 90 degrees from each other, and when one coil current is around 0 degrees or 180 degrees, a sufficient current flows in the other coil, and the currents around 0 degrees and 180 degrees do not significantly contribute to motor driving. Thus, a method of applying electricity is proposed in which the currents around 0 degrees and 180 degrees of the motor driving current are cut. For example, a method of applying electricity in which the application of electricity is cut for 30 degrees around 0 degrees and 180 degrees is known as 150-degree electricity application.
In order to execute the 150-degree electricity application, a circuit for generating a signal for such a configuration is required. There is also a demand for simplifying this circuit.